The present invention relates to improvements in repeater cases and design thereof for high density subscriber lines. Repeater cases have been known for years and the technology was well developed for T1 telecommunication lines. The cases are designed to hold sensitive telecommunications equipment in relatively unfavorable environments. In particularly, they are designed for installation in manholes or on telephone poles exposed to the weather. Accordingly, in order to protect the contents, the housing of the cases provide environmental protection and seal the contents from the impact of the environmental elements such as water, insects, and the like.
The repeater cases, which were originally designed to hold T1 line cards, have been used to hold HDSL modules. The HDSL modules work well in the T1 repeater case, except that it has been found that the modules prematurely fail due to excessive heat build up in the case. Premature failure adds considerably to the cost in having to replace the modules. The modules are fairly expensive in the first instance and replacement, of course, creates additional expense. There is also a problem of loss of reliability and performance arising from the premature failure. Obviously, when a module fails, it needs to be replaced and there is a cessation of service. If there are several module failures, the maintenance costs will also rise in addition to the cost of the module itself. There is a need in the art for a solution to the heat build-up problem in the HDSL cases.
In addition to the heat causing the electronics to fail, applicant has found another failure mode arising from high heats in the repeater case. The material of the connectors to which the cards are mounted fatigue, causing dimensional instability, warping and cracking. This, in turn can cause a loss of connection between the module and the connector, leading to performance failures.
The present invention fulfills one or more of these needs in the art by providing a repealer case for high density subscriber lines including a repeater base, a repeater housing having interior walls forming a sealed enclosure with the base, a plurality of module slots wherein the module slots are configured to receive HDSL-4 circuit board modules and wherein the HDSL-4 circuit board modules are cooled through thermal conductivity with thermally conductive contact with certain of the interior walls of the repeater housing. The thermally conductive material is not being required for structural support of the modules or their electrical functioning.
The apparatus may further include a cable inlet in the repeater case which has the capability to receive high density subscriber lines. The sections of the repeater case are made from a high temperature plastic. The repealer housing has a lid with an interior wall and typically includes a layer of thermally conductive material attached to the interior wall of the repeater housing lid. This layer of thermally conductive material preferably includes an exterior layer of aluminum foil on the top and bottom of the layer of thermally conductive material. A preferred thermal conductive material is G974 Therm-A-Gap material.
The repeater base of the repeater case can have up to twenty-five module slots to receive the HDSL-4 circuit board modules. The HDSL-4 circuit board modules further include connectors which are mounted to a circuit boards. These connectors are preferably made of a high temperature plastic, and the circuit board is preferably made of phenolic. The connectors, which receive the HDSL-4 circuit board modules are electrically connected to the cable inlet in the repeater housing case in conventional fashion through the phenolic board. The repeater case is typically comprised of three different sections, the repeater case, the repeater housing, and the repeater base.
After the HDSL-4 circuit board modules are mounted in the module slots and the connectors are connected to the high density subscriber lines via the cable inlet, the sections of the repeater case may be closed. A rubber gasket is placed between the repeater base and the repeater housing, and the repeater housing is bolted to the repeater base. Then, a rubber gasket is placed between the repeater case and the repeater housing lid, and the repeater housing lid is bolted to the repeater housing. When the repeater housing parts are connected, the repeater case is sealed and protects the HDSL-4 circuit board modules within from the environment. The interior of the housing may be pressurized in conventional fashion.
When the repeater housing lid is put in place, the thermally conductive material and the aluminum foil layer comes into contact with the tops of the HDSL-4 circuit board modules. When the lid is closed and tightened, the thermally conductive material compresses sufficiently against the HDSL-4 circuit board modules to make a good thermal transfer contact. The layer of thermally conductive material receives the heat generated by the HDSL-4 circuit board modules, and the heat is then distributed through the thermally conductive material layer. From there, the heat is radiated through the repeater housing lid to the outside, thereby keeping the heat build-up within the repeater case to a level which permits the HDSL-4 circuit board modules to operate and function without failure.
Preferably, the modules are mounted in high temperature connectors. The connectors are made of a plastic that can withstand the temperatures expected in the housing without fatiguing or deforming, and are, in turn, mounted to a phenolic circuit board.
The invention also provides a method of converting a repeater case so as to dissipate thermal energy from high-density subscriber lines including providing repeater case including a base, housing and lid; and installing a thermally conductive material in the lid sized so as to come into contact with the tops of HDSL modules mounted in the repeater case when the lid is mounted on the case. The method may include installing connectors for the HDSL modules in the case that are made of a plastic selected to withstand the expected operating conditions of the repeater case without warping.